The present invention relates generally to methods for determining anomalies in a line which is to be investigated, and more particularly to a method for determining anomalies in a line which is to be investigated in which a signal in the form of a pulse is applied to the line at one end, and a signal which is reflected in the line is detected at the same end of the line.
EP 0 433 020 A2 discloses a method of this type, in which each point of the reflected signal is sampled several times and an average value is formed to improve the accuracy of the method, preferably to avoid noise influences. In order to reduce the number of sample values to be taken into account in this case while increasing the measurement speed, the system noise on the one hand and the optical noise on the other hand are determined, for example on an optical line, before the start of the measurement; the variables determined for this purpose are fixed. After this, while carrying out the known method, the respective sample value is detected successively several times, the average value is formed, and the noise element in the result is calculated. If it is found that the noise was less than the predicted value (previously measured), then the sampling of this sample value is then set, and further evaluations are carried out to confirm whether the determined measurement allows an anomaly to be deduced in the optical line which is to be investigated.
Furthermore, DE-A-12 33 488 discloses an arrangement which operates in accordance with the pulse-reflection method for the determination of fault points or inhomogeneity points in an electrical line in the case of which an arrangement with a two-channel amplifier circuit is used for equalization of the reflected pulses in order to achieve exact measurement results taking into account the frequency-dependent attenuation properties of the electrical line which is in each case to be investigated. The amplifier circuit is arranged upstream of a bridge circuit, via a differential amplifier, which bridge circuit contains the electrical line to be investigated in one bridge arm and a line simulation in a further bridge arm; further bridge arms have non-reactive resistors. The bridge circuit results in only the reflected pulses being detected on the output diagonal by the differential amplifier, and being passed on to the equalizing amplifier circuit, when test pulses are applied to the input diagonal. Pulses which allow a reliable deduction to be made on the magnitude and range of a fault on the electrical line which is to be investigated are produced at the output of the amplifier circuit, which is of relatively complex construction.
The present invention is directed to the problem of developing a method for determining anomalies in a line which is to be investigated, in which the measurement result can be achieved with high accuracy and in a relatively short period of time.